Bone fracture is a traumatic disruption of the continuity of the bone structure. If there is relative motion of the bone fragments at the fracture site, proper alignment and rejoinder of bone fragments may not be achieved, and the time of fracture healing is usually extended. Disruptions from congenital defects or fractures of the complex and relatively thin bone structures surrounding and supporting the human eye or globe present difficult internal bone repair and fixation problems in reconstructive surgery and in trauma surgery.
The so-called orbital margin comprises a protective bone boundary for the globe. The margin is stronger than the bone structure which forms the orbital walls. If the eye is struck with a relatively round object, i.e., a baseball, a tennis ball, an elbow or a fist, the margin or rim of the orbit, which can withstand considerable force, diffuses the object's impact. However, compression of the orbital contents may occur and produce a "blow-out" fracture of the orbit involving the floor and/or the lateral and medial orbital walls and may result in major destruction of the entire orbit. Also, direct injury at the lateral orbital rim may produce a "tripod" fracture. When significant portions of the internal orbit are disrupted, standard bone-grafting techniques for immediate and post-trauma orbital reconstruction may not result in predictable eye (globe) function and positioning. Critical bone support of the globe by bone-grafting is frequently deficient as a result of bone graft displacement, undercorrection, over correction, or inadequate initial reconstruction of the orbital volume, or ultimate bone-graft resorption.
The superior wall or roof of the orbit is triangular in shape and is formed of two bones. The bulk of the orbital roof consists of the orbital plate of the frontal bone with the lesser wing of the sphenoid making up the posterior portion. The anterior one-half of the orbital roof is relatively thick and forms the floor of the frontal sinus. Posteriorly, the roof of the orbit is thinner and is joined to the medial wall by the frontoethmoidal suture. The orbit roof is separated from the lateral wall of the orbit by the zygomaticofrontal suture anteriorly and the superior orbital fissure posteriorly.
The medial orbital wall is oblong in shape, and is comprised of four bones, i.e., the frontal process of the maxilla, the lacrimal bone, the lamina papyracea of the ethmoid, and the sphenoid. The bulk of the medial wall consists of the very thin and delicate lamina papyracea. Anteriorly, the medial wall of the orbit consists of the maxillary process of the frontal bone and the fossa for the lacrimal sac. The fossa for the lacrimal sac is formed by the frontal process of the maxilla and the lacrimal bone. The lacrimal bone is divided into two portions by a vertical ridge, the posterior lacrimal crests. Posterior to the crest, the lacrimal bone is flat and articulates with the lamina papyracea and the ethmoidal air cells. Anterior to the posterior lacrimal crest, the lacrimal bone becomes thinner and forms a portion of the fossa for the lacrimal sac. The anterior portion of the fossa for the lacrimal sac is formed by the frontal process of the maxilla, which forms the anterior lacrimal crest. The posterior aspects of the medial orbital wall is comprised of a portion of the body of the sphenoid bone.
The inferior orbital wall or floor is comprised of three bones, i.e., the maxilla, the zygomatic, and the palatine. The majority of the orbital floor is formed by the orbital plate of the maxilla. The shape of the inferior orbital wall or floor approximates an equilateral triangle. The orbital floor extends only about two-thirds of the depth of the orbit and does not extend to the orbital apex. The inferior orbital rim and the adjacent anterior portion of the orbital floor are strong in comparison to the thinner portions of the orbital floor. It is not surprising that a traumatic blunt force applied to the orbit compresses the orbital contents and often results in fracture of the orbital floor.
The lateral orbital wall is triangular in shape and is comprised of the zygomatic bone and the greater wing of the sphenoid. In the posterior orbit, the boundaries of the lateral orbit wall are defined by the superior and inferior orbital fissures. The lateral orbital wall is flat and is directed at a 45 degree angle from the medial orbital wall. The lateral orbital wall is the strongest of the orbital walls due to the prominent zygomatic bone but presents a series of alternating strong and weak areas.
As has been noted above, fractures of the internal orbit are commonly seen as the result of blunt force blows or trauma to the face. These fractures may occur as isolated blow-outs or may be associated with multiple facial fractures. The degree of destruction of the internal orbit may range from a small defect in the floor to destruction of all four walls of the orbit. The recommended treatment of these injuries varies greatly. Surgical treatment has ranged from packing of the maxillary antrum to total orbital reconstruction with autogenous or synthetic materials. Accurate anatomical reconstruction of the bony orbit is essential to maintain normal function and appearence of the eye following orbital fractures. Because most of the bone in the internal orbit is thin, it is frequently difficult to reduce and adequately stabilize the fractured bone fragments without the use of autogenous or alloplastic materials.
Historically autogenous bone grafts have been the material of choice for most craniomaxillofacial surgeons for the reconstruction of the internal orbit. Split membranous bone from the calvarium and other autogenous materials including iliac bone, split rib bone and catrilage have been used as bone graft materials. Such materials, however, have yielded an unpredictable amount of resorption, particularly in the posterior half of the orbit. When significant resorption occurs, there is increased displacement of the globe.
A variety of alloplastic materials such as silicone ribber, Teflon, Supramid, tantalum mesh, Vitallium mesh, titanium mesh, polyethylene, and methyl methacrylate have been used for orbital reconstruction. Over the past ten years there has been an increasing interest in, and use of, perforated biocompatible metallic strips and panels as a means for rigid internal fixation of fractures in trauma surgery and as a plate material for bone part immobilization and stablilization and bone graft support material in reconstructive surgery. Of particular interest has been the use of perforated strips and panels fabricated of totanium as an unequaled implant material in use clinically for over 30 years with no documented cases of adverse reactions. Pure titanium is the material of choice in craniofacial reconstructive surgery when non-removal of the implant is indicated. As an implant material, pure titanium is preferred because its low density (weight) and elastic modules (stiffness) are approximately one-half that of stainless steel or cobalt-chromium alloys and the material is corrosion resistant and pliable. Further, bone plates made of perforated titanium strips and perforated titanium panels can be cut to appropriate configuration and contoured at the time of surgery and, when affixed to bone fragments or bone parts with bone screws, provide solid, stable fixation means during trauma surgery and planned reconstructive surgery.
A preferred form of perforated titanium strips and panels (titanium mesh) includes rows of substantially square perforations which are formed in titanium sheet material. The use of titanium mesh with square holes for internal fixation of bone fractures and for reconstructive surgery provides the surgeon with an implantable plate material which can be easily cut to desired contour and shaped or bent to conform to bone fracture and reconstruction sites.
It is a principal object of the present invention to provide a unique perforated metallic plate structure for the internal repair of orbital defects and fixation of orbital fractures.
It is a further object of the invention to provide a unique perforated metallic implantable plate structure which is preshaped and ready for use in surgical procedures relating to the repair of the medial and lateral walls and the floor of the orbit.
It is still a further object of the invention to provide a unique orbital repair implant plate structure of preshaped contour for use in the surgical internal fixation of orbital fractures.
It is yet another object of the invention to provide a perforated metallic orbital repair implant structure of preshaped configuration which can be readily cut, reshaped or bent to conform to the orbital walls and affixed to the orbital margin or rim.
Other objects and advantages of the invention will be apparent from the following summary and detailed description of the orbital repair implant structure of the invention taken with the accompanying drawing figures.